Realization of Quantum Maxwell’s Demon with Solid-State Spins ^*

Abstract

Resolution of the century-long paradox on Maxwell's demon reveals a deep connection between information theory and thermodynamics. Although initially introduced as a thought experiment, Maxwell's demon can now be implemented in several physical systems, leading to intriguing test of information-thermodynamic relations. Here, we report experimental realization of a quantum version of Maxwell's demon using solid state spins where the information acquiring and feedback operations by the demon are achieved through conditional quantum gates. A unique feature of this implementation is that the demon can start in a quantum superposition state or in an entangled state with an ancilla observer. Through quantum state tomography, we measure the entropy in the system, demon, and the ancilla, showing the influence of coherence and entanglement on the result. A quantum implementation of Maxwell's demon adds more controllability to this paradoxical thermal machine and may find applications in quantum thermodynamics involving microscopic systems.

Spin-driven electrical power generation at room temperature

“…A quantum thermodynamical theory along a similar spintronic path has been proposed 8 , while classical electronic implementations using capacitively coupled quantum dots have been demonstrated at low temperature 3,5,63 . Our results should thus generate research initiatives on quantum electronic circuits at the rather unexplored intersection between quantum thermodynamics [3][4][5][6][7][8][9][10][11][12] and spintronics 20,34,54 . More generally, our work also indicates that the high transport spin polarization, and low density of states, of spinterfaces represent a compelling approach to integrating the quantum properties of nano-objects within a solid-state device's operation at room temperature, beyond proof-of-concept electronic decoupling strategies 43,64 .…”

“…Inspired by the report of Miao et al 2 , and by recent progress in quantum thermodynamics [3][4][5][6][7][8][9][10][11][12] , we propose that a spin-split paramagnetic (PM) quantum object can enable electrons with a spin ↑ or ↓ quantum property to flow in opposite directions if the transmission rates on either side of the PM center are spindependent. Differing amplitudes in these transport spin channels generate a spontaneous current flow.…”

“…These heat and information engines are driven by fluctuation-induced quantum tunneling on/off of QDs, with a transmission asymmetry between left and right leads that can be energy-dependent due to the QD's discrete energy levels 6,7 . A few reports have theoretically 8 and experimentally (using nitrogen vacancies in diamond 9 ) taken into account the electron spin.…”

Verification of Information Thermodynamics in a Trapped Ion System

“…For instance, Maxwell’s demon can be used to design an engine to extract work from quantum measurements [ 12 , 13 ], to realize a steering heat engine in quantum systems [ 14 ], and to appear in nonequilibrium systems [ 15 ]. Besides, Maxwell’s demon has been produced in different physical systems, such as the superconducting quantum circuits [ 16 ], ultracold atoms [ 17 ], and solid-state spin degrees of freedom [ 18 ]. Meanwhile, the quantum version of Léo Szilárd engine has also been proposed in Ref.…”

Szilard Engines as Quantum Thermodynamical Systems

“…While originally formulated in the classical domain, the inherent microscopic character of these analyses, together with the dramatic improvements in our ability to manipulate systems at the nanoscale, forces us to re-examine these engines to account for quantum behavior. Indeed, descriptions of the quantum version of Szilard's engine have been widely discussed [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] and also experimentally realized [29][30][31][32][33][34][35]. While a fully accurate description of engine operation requires accounting for the details of the underlying dynamics, the following focuses on two aspects of the quantum Szilard engine.…”